Hi everyone. I had used V5 a couple of years ago and recently restarted with V7. In my project have some traces that I need to solder coat so I selected “Add a rule area”. I selected the B Mask, (which is where the traces are that I need to expose) and then left the defaults in the pop-up box. I then drew around the trace area to be exposed and the hatched area popped up. I then selected the arrow tool, pulled up a 3D view and in the area that should have the mask removed still has the mask in place. I went to my V5 machine and a similar sequence worked perfectly. I have spent about five hours trying different things in V7 and nothing has worked. When researching the problem I saw a few reasons and remedies but nothing has worked. I am very confused because it worked perfectly in V5 but not 7. Has anyone found a solution to this problem? Thanking you ahead of time. Chris.
I just tried it on a board. If you don’t type b to actually fill the area, it won’t show on the 3D preview. I think in v5 filling was immediate. Now you need to type the “fill” key.
Thank you, so I select the arrow, then highlight the “box” that I created (drew) in the tool and then hit b or is it just after the box is created and I’m still in the tool that I am supposed to hit b? I thought I had tried both ways but I was pretty tired and may have dreamed it. 
I will work with it later today and report back if I don’t hear from you first. I more than appreciate your reply.
As long as the hatched outline is there you can fill the box with b, no need to hold onto the mouse button. You can even draw other boxes and the hatched outlines will appear, then fill all of them in one go with b.
The instructions in the documentation talk about filling copper zones but it applies to other layers too.
PS: For your usage make sure Solid Fill is selected in the popup dialog box, there are other types of fills.
I think you have to use the “draw filled zone” command, not the “Rule area” tool.
I’m Using v7
Showing Copper Zone/Layer but, could do on Mask Layer… these are older videos…
Two Video demo’s - (1)Drawing Shape with Creating Net, (2)Additional Demo…
• Shapes drawn in the PCB editor but, could import Shapes if wanted
• Multiple Zones, each belonging to different Net’s
(you don’t need Net’s)
• Three are previously Filled (color reflects the Layer’s Color)
• Un-fill’s them and Re-Fill’s them
• Three not previously Filled so, I Fill them
Can Fill/Un-Fill individually or All…
Not Shown: If you want to have a Connection (such as a Terminal or some Part, place them into the shape Before Filling
Okay,
1)It is necessary to select F Mask or B Mask depending on where the track is that you’re working with.
2)After that click on “Add a fill zone”.
3)Draw the mask on the area that you want to be removed.
4)Directly after drawing, put the mouse over the hatched area and hit b. (A very fast popup will come up saying that it is filling).
After these steps you will have the corresponding view in 3D.
I just ran through the steps so that if someone with the same question in the future can understand step by step how to do this. I thank everyone who chimed in for the help. I can now happily proceed with my project.
I have no KiCad here so can’t check it, but why you use fill zone (and previously rule area) and not just a graphic figure (I suppose KiCad have filled polygons).
Filled zone is a complicated tool/thing that know how to fill itself preserving the specified clearances to other nets, minimum width (when filling goes between pads) making thermal relief connections, deleting islands (if specified so) and so on. All these is not needed in your case. I, generally, have a habit to not use a cannon to shoot down a sparrow so am surprised if someone else does it. May be there are some advantages of filled zone than I just don’t know.
I am even surprised that fill zone can be used at no copper layer. Do all its functionality is just not used?
Hi Piotr,
I am far from any expert but I will say that the method that I have outlined is very simple. It is the way I have learned to do it from the helpful people here. It seems very basic… Just tell the program that you want to unmask, draw and then hit “b”. I do not think it is more complicated than any other method. I had about twenty tracks to unmask. Once everything is set up with a few clicks you can do many in succession. There are many here that are far more experienced with KiCad and perhaps they can reply better. Thank you for your concern.
You can also draw lines on the mask layers to unmask these parts.
In 7.0+ it is also possible to convert selected tracks to zones (or polygons) by using this menu (you have to be on one of the mask layers for the correct dialog to appear):
Then refilling the zones.
I didn’t know that it is able to unmask only tracks. I supposed that the whole zone you specify is unmasked. As I said I have no KiCad here (at home I have Win7 so KiCad V5) so was no able to do any checks today.
In near future (maybe 3 months from now) the easiest way will be this:
Just select the wanted tracks, open Properties and choose the Solder mask.
You don’t need to put the mouse on the hatched area or do it directly after drawing. B are any time will fill any latent zones.
There is actually a setting to get the old behaviour of automatically filling after drawing but this slows down the program especially for copper zones.
Yes, I noticed that after my post. Thank you for the clarification.
Fill zone is actually a general operation that can work on different layers even though the documentation only talks about copper. (Maybe the documentation should be augmented.) On silkscreen it creates an area filled with paint (I think it can also be hatched). On mask, because this layer is subtractive, it actually removes mask rather than filling.
Thank you for the info. I have an upcoming project that that will be useful in. The more I learn, the more I learn that I don’t know. 
Are you saying that if I select “line” and give the line a width of the track it will accomplish the same unmasking? If I understand this correctly the unmasked area will then perfectly match the track, making the unmasked area exactly the same as the track?
Yes. -----------------